Aquatic gliding board having a deck with a sandwich structure with an elastic core

ABSTRACT

An aquatic gliding board, or float, which includes a core covered with an outer casing forming a deck and a hull thereof. The outer-casing includes at least one deck portion and one hull portion, at least the deck portion of the casing having a sandwich structure which includes at least one low-density core between two thinner layers having high mechanical characteristics including layers of resin-impregnated fibers, with the low-density core of the sandwich structure of the casing of the deck portion including a flexible and elastic cellular material.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 of French Patent Application No. 05.05875, filed on Jun. 9, 2005, the disclosure of which is hereby incorporated by reference thereto in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field of aquatic gliding boards, or floats, such as surfboards of boards for windsurfing.

2. Description of Background and Relevant Information

Conventionally, a surfboard and other types of aquatic boards or floats are made from a block of foam, such as a rigid polyurethane foam blank that is formed in a mold. The foam blank is machined by planing and sanding in order to locally customize its shape and thereby form the core of the float/board. This machined core is then covered with a resin-impregnated glass fiber layer that forms an outer reinforcement shell and gives the board its final shape and its mechanical strength. A decoration and a glaze coating give the board its final appearance.

In some cases, the core is longitudinally cut into two portions, which are then glued to a wood stringer which reinforces the structure of the core.

One of the drawbacks of this conventional construction method is the final weight of the finished board. Indeed, the foam is relatively dense: typically, its bulk density is about 50 kg/m³, and it is, a priori, not possible to reduce the foam density without negatively affecting the mechanical properties of the board.

In the field of “bodyboards,” the float is mainly made of elastic foam (such as by associating several layers having various densities and characteristics) without having an outer casing with high mechanical characteristics. In some cases, such floats are provided with a lower thermoformed plastic layer to ensure better gliding on water. However, these boards are generally relatively flexible as the user must be able to deform them during use for better maneuvering. Unlike boards for surfing and windsurfing, on which the user stands, bodyboards are not required to withstand substantial forces because the user operates such a board while lying down facing the water surface with only his/her torso supported on the board.

According to another method of construction originating from the field of windsurfing and sailboards, one starts with a rigid foam blank with a relatively low density (for example an 18 kg/m³ expanded polystyrene foam), which is machined to shape, or molded directly to the shape of the core of the float/board. The core is covered with an outer layer, or casing, which can take the form of a resin-impregnated glass fiber skin, and/or a sheet of thermoformed plastic material, and/or a sandwich structure. Such a construction method can allow for more weight while maintaining a good rigidity, especially when a sandwich structure casing is used, that is, a structure including a low-density layer (generally a PVC or an extruded polystyrene foam) located between two thinner layers having high mechanical characteristics (such as resin-impregnated fiber). Such a construction, when using sandwich structures, enables one to achieve rigid, and therefore potentially efficient boards, but sometimes at the expense of comfort and maneuverability.

According to other techniques, a gliding board can be constructed to include a central core made of a first cellular material covered by a layer of rigid, more dense and stronger cellular material, itself covered by an outer skin, such as a thermoformed plastic sheet or resin-coated layer of fibers, as disclosed in the patent documents WO 82/04023 and DE 33 11 734.

It is also known to make hollow gliding boards having a sandwich structured casing. For example, two half-shells can be made, which are then assembled to one another, or, alternatively, the entirety is made in a closed mold having an inner bladder that is inflated to push and apply the sandwich structure against the walls of the mold.

It is also known to make gliding boards that include a rigid inner structure covered by an outer layer of flexible foam, which determines the outer form of the board, as disclosed in U.S. Pat. No. 3,543,315 and U.S. Pat. No. 5,489,228. These boards are generally very comfortable during navigation, but they are too heavy and the flexibility of their outer casing does not yield good results in terms of responsiveness and steering accuracy of the board. Indeed, the layer of flexible foam is only covered by a plastic film or a flexible casing having no notable mechanical strength, the only role of which is to protect the flexible foam from abrasion and to improve gliding.

In addition, gliding boards have been proposed which have a different hull and deck structure. The patent document FR 2 787 088 provides for a gliding board that includes a foam core covered by a casing. On the deck, the casing is a rigid sandwich structure, whereas for the hull, the casing is a mere layer of resin-impregnated fibers. In the patent document FR 2 612 874, the hull of the board is covered with a thin layer of elastic material so as to give it shock-absorbing properties. Conversely, in the patent document DE 32 06 334, it is the deck of the board that is covered with a layer of elastic material. In the two latter cases, the layers of elastic material are directly exposed to the outside.

The patent document DE 197 41 917 discloses a plurality of constructions in which the casing of the board has a layer of resin-impregnated fiber associated with a layer of damping material. Various options are provided, but it is always provided for the damping layer to be arranged on the outside with respect to the layer of resin-impregnated fibers. However, the damping layer is provided to be located either solely on the deck, or on the deck and on the hull of the board. This document does not envision using a sandwich structured casing.

SUMMARY OF THE INVENTION

The invention provides for an aquatic gliding board, or float, which includes a core covered by an outer casing forming a deck and a hull for the board, in which at least the deck portion of the casing having a sandwich structure including at least a low-density central layer between two thinner layers with high mechanical characteristics, in which the high mechanical performance layers include layers of resin-impregnated fibers, and in which the central, low-density layer of the sandwich structure of the deck portion includes a flexible and elastic cellular material.

In a particular exemplary embodiment, the aquatic gliding board of the invention includes a core covered with an outer casing forming a deck and a hull, in which the outer casing includes at least a deck portion and a hull portion, both made in the form of a sandwich structure made, for each of the portions, of at least one low-density central layer between two thinner layers having high mechanical characteristics, in which such high mechanical performance layers include layers of resin-impregnated fiber, in which the low density central layer of the hull portion is made out of rigid cellular material, and in which the low-density central layer of the deck portion includes a flexible and elastic cellular material.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will become apparent upon reading the following description, with reference to the attached drawings, and in which:

FIG. 1 is a top schematic view of a float/board according to a particular exemplary embodiment of the invention;

FIG. 2 is a cross-sectional schematic view along the line II-II of the of FIG. 1;

FIG. 3 is an enlarged and exploded partial view of FIG. 2;

FIG. 4 is a cross-sectional partially cut-away schematic view showing an embodiment for a stiffening reinforcement.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows the general outer form of a float 10 for gliding on water, such as a surfboard or a sailboard, for example. Hereinafter, the float will be referred to as a board or a gliding board. FIG. 2 shows an embodiment of the invention in which the board includes a core 14 arranged inside an outer casing 12. In a known manner, the upper portion of the outer casing 12 forms the deck 16 of the board adapted to support the user, and in its lower portion, the hull 18 faces the water. The peripheral lateral surface/edge of the outer casing defines the rails of the board. This outer casing defines, in a watertight manner, an inner space of the board that is entirely or partially filled by the core.

The core can be made, as one example encompassed by the invention, using an expanded polystyrene foam having very low density, for example, a bulk density lower than 25 kg/m³, or even equal to or lower than 18 kg/m³.

The core 14 can also include localized reinforcements, made out of a particularly strong material, which extend along the entire height of the inner space demarcated by the casing, or along only a portion of this height. An example of such a core is described hereinafter, with reference to FIG. 4.

In the example shown, the core 14 entirely fills up the inner space of the board. However, it could also be provided that recesses be included so as to leave hollow inner zones inside the outer casing 12, for example, at the front of the board, which is a zone on which the user generally applies very little force since the surfer typically does not apply his/her weight to the front zone. The presence of hollow zones favorably reduces the weight of the board, and their distribution affects the dynamic moment of inertia of the board, which influences its behavior on water, particularly its responsiveness to the various forces and changes of direction applied by the user.

Out of simplicity and cost-efficiency, the exemplary core 14 shown in the drawing figures is a unitary element made out of a single material. However, the core could be made from a plurality of elements, possibly made of various materials.

In addition, the core could be made to include a plurality of holes or recesses to lighten the core. Similar methods to lighten the core, such as those described in patent documents FR 2 820 712, FR 2 820 713, and FR 2 820 714, could be advantageously implemented and, therefore, are encompassed by the invention.

In this embodiment of the invention, the two portions (deck and hull) of the casing have a sandwich construction in which a layer of low-density material forming the core 24, 25 of the sandwich structure is confined between an inner layer 26 and an outer layer 28 of reinforcement material that form the skins of the sandwich and include, for example, layers of fiber embedded in resin, for example epoxy resin. The type of fibers (glass, carbon, aramid, etc.) can be identical or different for the inner and outer layers. Similarly, it can differ between the hull portion and the deck portion, meaning, for example, that one can provide for the inner layer of the deck to include aramid fibers, whereas the inner layer of the hull would include carbon fibers. In the same way, the layers of fibers can be woven or non-woven, unidirectional or multidirectional. For the simplest and most cost-effective constructions, the layers of fibers are glass fiber fabrics.

However, in this particular exemplary embodiment of the invention, the deck and hull portions of the casing differ in the type of material of which the core 24, 25 of their sandwich structure is constituted. In the hull portion, the low-density material layer 25 is made of one or several materials referred to as “rigid”, whereas in the deck portion, the low-density material layer 24 includes, according to the invention, at least one portion made of a flexible cellular material. In relative terms, of course, the material(s) of layer 25 are more rigid than the material(s) of flexible layer 24, and the material(s) of layer 24 are more flexible than the material(s) of rigid layer 25.

In particular exemplary embodiments of the invention, the low-density materials are cellular materials, such as foams made of plastic materials.

One having ordinary skill in the art usually classifies plastic material foams as flexible foams, on the one hand, and as rigid foams, on the other hand.

The rigid foams have low elasticity in the sense that as soon as the compression force exceeds a certain value, they deform by collapsing in an irreversible manner, or only a slightly reversible manner. Examples of rigid foams are polyurethane foams and extruded polystyrene foams or expanded polystyrene foams, which are generally used in the form of foam blanks to form the cores of conventional surfboards. Similarly, some PVC or polyimide foams, generally used as cores in sandwich structures, are considered as rigid materials. Although referred to as rigid, these foams, in the lowest densities, can be quite easily compressed (and can therefore appear to be soft), yet they have very low elasticity.

Flexible foams made of plastic material having elastic properties, such as expanded polyolefin foams, particularly polypropylene and polyethylene foams, are among those known as flexible cellular materials. In the case of expanded polypropylene foams, grades having bulk densities between 20 and 100 kg/m³, for example, can be used These materials generally have a 25% compressive deformation stress, ranging from 100 to 600 kPa. Considerations in choosing a material are its compressive strength, but even more so, its capacity to deform elastically (the material will preferably recover its initial shape after a compression of 25% or about 25%), and its capacity for restoring the energy absorbed during the compression.

In addition to the foregoing, the invention encompasses the use of other materials. In this regard, for the hull, the rigid foam 25 can be replaced by a honeycomb structure, or by a layer of wood, such as a light-weight wood.

Using a rigid core 25 for the sandwich structure of the hull makes it possible to achieve a substantial rigidity for the hull, which promotes good acceleration capabilities and a very precise steering of the board. In less elaborate alternative embodiments of the invention, the hull portion of the casing can have another structure. For example, the hull can be a mere layer of resin-impregnated fibers, or an intermediate layer of a light and rigid material (rigid foam, light wood, etc.) covered with a layer of resin-impregnated fibers.

The use of a flexible material to form the core 24 of the sandwich structure of the deck is particularly innovative. Indeed, by choosing the right rigidity for this flexible material, one can take advantage of the exceptional rigidity-to-weight ratio of the sandwich structure while inserting, in the area of the deck, a surface flexibility that is particularly advantageous in terms of comfort and ease of steering the board.

This is due to the fact that the outer skin 28 of resin-impregnated fibers, which intrinsically has high elastic properties, can deform under the forces applied by the user without causing the collapse of the core material 24, which is also elastic, and then return to its original position while restoring a major portion of the stored energy. The outer skin 28 is then biased both in flexion and traction, along its surface, like a trampoline. Thus biased, the outer skin 28 made of composite material, allows for restoring much more energy than the mere elastic return of a plastic material, which would be arranged on the deck of the float and which would be vertically compressed. By comparison, the “trampoline” effect with a high elastic component can be opposed to a mere “mattress” effect that is mainly damping, and which therefore tends to restore only a small portion of the energy that is transmitted to it. The trampoline effect makes steering the float much more lively.

This deformation/restitution effect of the outer skin 28 of the sandwich is completely reversible (at least up to a certain limit that can be determined, for example, by varying the thickness and the rigidity of the outer skin 28 and/or by varying the rigidity of the flexible elastic material forming the core 24 of the sandwich structure), and it occurs without causing any notable deformation of the core 14, due to the presence of the layer 26 of resin-impregnated fibers under the flexible and elastic layer. The layer of resin-impregnated fibers, in addition to its own mechanical strength, makes it possible to distribute the stress transmitted thereto over a large surface.

In addition to the advantage in terms of vivacity, or liveliness, the sandwich construction with elastic core enables the deck to better withstand impacts and caving-in effects. To improve the trampoline effect, the resin of the outer skin (for example an epoxy resin) can possibly be mixed with compounds that improve its flexibility.

It can be seen from the example shown that the layer of flexible foam 24 that forms the core of the sandwich structure of the deck extends downwardly along the lateral edges of the board. This especially makes it possible to take advantage of the better impact resistance of this structure in a particularly exposed zone. One could provide for the sandwich structure 25 of the hull of the float to rise along the lateral edges, for the two structures to meet at the widest point, or for the lateral edges to have their own structure.

Various methods for manufacturing a board according to the invention are encompassed by the invention.

The outer casing 12 can be manufactured in the form of two prefabricated half-shells forming the deck and the hull, respectively, of the board, the half-shells being assembled to one another, for example by gluing, along their parting line, to form a watertight outer casing.

In an alternative embodiment, the two half-shells can be assembled one to the other before the reinforcement outer layer is applied on the layer forming the core of the sandwich. Such a method is similar to that described in the patent document WO 02./10011 and family member U.S. Pat. No. 6,736,689, the disclosure of the latter of which is hereby incorporated by reference thereto in its entirety, and which advantageously provides an opportunity to rework the layer forming the core of the sandwich after assembling the half-shells, but before applying the outer layers of the sandwich, in order to customize the shape of the board, if desired.

According to another method of construction, all of the components can be assembled and shaped under pressure in a mold, according to the technique usually used for the manufacture of windsurfing boards of the sandwich type.

In the example shown in the drawings (see, e.g., FIG. 3), it has been provided for the outer casing 12 to further include an outer protection made in the form of a sheet 30 of thermoformed thermoplastic material. This protective layer 30 is translucent, for example, and can be decorated. The decoration can advantageously be arranged on the side of the sheet that is turned toward the inside, and can be made, for example, by silk-screening or by sublimation. Also a decoration element can be incorporated between the outer skin 28 and the protective sheet. The protective sheet can be made out of a material including a mixture of ABS and polyurethane, for example, and have a thickness of about 0.3 mm. The protective sheets could possibly be different on the deck and on the hull of the board. Such a protection layer be arranged on only one side of the board, for example on the deck.

FIG. 4 shows an embodiment of a reinforcement 32. This reinforcement 32 is simply made of a sheet of resin-impregnated fibers folded over itself to form a T-shape, the vertical arm 34 of which is inserted in a groove 36 formed in the core 14, and the horizontal portion 38 of which rests against an upper surface of the core 14. To this end, a rectilinear groove 36 substantially perpendicular to the outer surface of the core is arranged in the core. The sheet of resin-impregnated fibers (not yet polymerized and therefore still flexible), is folded over in two and inserted at the hull of the groove 36. The portions of the sheet which project outwardly are then folded back against the outer surface of the core. Once the resin has been polymerized, the reinforcement 32 forms a rigid T-shaped profile, which is integrated into the core 14. The vertical portion 34 of the T-shape gives it a very good flexural strength, whereas the horizontal portion 38 forms a kind of plate that allows the distribution of the pressures exerted locally by the outer casing 12 on the core 14. Thus, this reinforcement 32 is particularly advantageously placed on the board's deck as it reinforces the core where the strong pressures applied by the user are exerted. FIG. 1 shows a possible arrangement with two reinforcements 32 arranged on the deck, on each side of a median longitudinal axis of the board. A reinforcement of this type could also be used on the hull of the board to take full advantage of its flexural strength.

In the example of FIG. 4, the reinforcement 32 is positioned on the exposed core 14. However, to facilitate this operation, the reinforcement could be positioned after having coated the core with the inner skin 26. The main difference is that the horizontal portion 38 of the T-shape of the reinforcement is then arranged between the inner skin 26 and the low-density layer 24, 25.

The construction according to the invention therefore provides for the manufacture of an aquatic board, such as a surfboard or sailboard, which offers a perfect compromise between ease and steering precision, comfort and performance, all of which are achieved with a method of construction well-suited for industrial implementation, allowing relatively low production costs.

Moreover, based upon the foregoing description, the invention provides for a new optimized construction for the manufacture of an aquatic gliding board, such as a surfboard or a tailboard, which enables an easy and low-cost implementation, a limited final weight for the board, while achieving a sufficient overall stiffness for good performance, as well as a guaranteed comfort of use, without sacrificing either steering precision or structural integrity. 

1. An aquatic gliding board comprising: a core; an outer casing covering the core, said outer casing comprising: a deck portion; and a hull portion; at least the deck portion of the outer casing comprising a sandwich structure, said sandwich structure comprising. at least one low-density core layer between two thinner layers; the low-density core layer of the sandwich structure comprising a flexible and elastic cellular material; each of the two thinner layers having a higher strength and stiffness than the core layer of the sandwich structure; each of the two thinner layers comprising a layer of resin-impregnated fibers.
 2. An aquatic gliding board according to claim 1, wherein: the low-density core layer of the sandwich structure of the deck portion of the outer casing comprises a polyolefin foam.
 3. An aquatic gliding board according to claim 2, wherein: the low-density core layer of the sandwich structure of the deck portion of the outer casing comprises a polypropylene foam.
 4. An aquatic gliding board according to claim 1, wherein: the material of the low-density core layer of the sandwich structure of the deck portion of the outer casing has a 25% compressive deformation stress, ranging from 100 to 600 kPa.
 5. An aquatic gliding board according to claim 1, wherein: the material of the low-density core layer of the sandwich structure of the deck portion of the outer casing has an elastic deformation recovery capacity such that initial shape of the material is recovered following a compression of 25% or about 25%.
 6. An aquatic gliding board according to claim 1, wherein: the sandwich structure of the deck portion of the outer casing extends downwardly along lateral sides of the aquatic gliding board.
 7. An aquatic gliding board according to claim 1, wherein: the sandwich structure of the deck portion of the outer casing is covered with a protective layer made of thermoformed plastic material.
 8. An aquatic gliding board according to claim 7, wherein: the protective layer is transparent; and an inner surface of the protective layer includes a decoration.
 9. An aquatic gliding board according to claim 1, wherein: the hull portion of the outer casing comprises a sandwich structure, said sandwich structure comprising: at least one low-density core layer between two thinner layers; the low-density core layer of the sandwich structure of the hull portion of the outer casing comprises a rigid material; each of the two thinner layers of the sandwich structure of the hull portion of the outer casing having a higher strength and stiffness than the core layer of the sandwich structure of the hull portion of the outer casing; each of the two thinner layers of the sandwich structure of the hull portion of the outer casing comprising a layer of resin-impregnated fibers.
 10. An aquatic gliding board according to claim 1, wherein: the hull portion of the outer casing comprises at least one layer of resin-impregnated fibers, said at least one layer of resin-impregnated fibers covering an intermediate layer of rigid material.
 11. An aquatic gliding board according to claim 1, wherein: the core of the aquatic gliding board is made of expanded polystyrene foam.
 12. An aquatic gliding board according to claim 1, wherein: the core of the aquatic gliding board comprises recesses.
 13. An aquatic gliding board according to claim 1, further comprising: a protective layer made of thermoformed plastic material covering an entirety of the aquatic gliding board.
 14. An aquatic gliding board according to claim 12, wherein: the protective layer is transparent; and an inner surface of the protective layer includes a decoration. 